802.3af (PoE) provides up to 15.4W at the source — standard for fixed cameras and access readers. 802.3at (PoE+) reaches 30W — for motorized cameras, illuminators, and small PTZs. 802.3bt (PoE++/4PPoE) reaches 60-90W (Type 3 and Type 4) — for multi-imager cameras, large outdoor PTZs, and devices with integrated heaters. Match the injector class to the device's PoE rating; over-spec'd injectors don't harm devices but cost more.

Cat5e supports 802.3af and 802.3at to the full 100 m run length without issue. For 802.3bt at 60W+ over long runs, Cat6 with shielded conductors is more reliable — Cat5e can deliver but voltage drop approaches the limits of the spec. For new installs, Cat6 is the safe baseline; for retrofits over existing Cat5e, validate end-to-end voltage at the device after installation.

The IEEE standard caps PoE at 100 m on copper. PoE extenders (Veracity Outreach, Phybridge UniPoE, ComNet PoE extenders) regenerate the signal at intermediate points and stretch the effective run to 300-1000 m depending on the product. For runs beyond 100 m on a single segment, fiber-to-the-camera with media converters is often cheaper than chained extenders.

If your PoE switch has sufficient per-port budget and total PoE budget for all connected devices, no — the switch handles power delivery. Injectors are needed when (a) the existing switch is non-PoE and replacing it isn't viable, (b) a single device needs higher PoE class than the switch supports, or (c) the device is placed far from the switch and a local injector with shorter run is preferable.

Only if the switch port delivers 802.3at (PoE+) or higher. A pure 802.3af port (15.4W max) cannot reliably power an 802.3at device that needs up to 30W — the device will fail to negotiate or will reset under load. Confirm the switch's per-port PoE class capability in its datasheet, not just the aggregate PoE budget. Many older switches are af-only despite total-budget numbers that suggest otherwise.